If you have a reservation (I do) and you show up 30 minutes after opening time (9am) will you still get in? Or do you have to be there before (or right at the time that) the gate opens?

Yes, I dont see any problem in it.

I saw people showing up right until the cut off. You really want to make the most of it though

You're good to go in!

Yes you can get in all the way up to an hour before they start to let in the 2o'clock reservations

As long as you arrive during your reservation time, you'll be admitted.

When I went there, I got right when they opened. My friends were late and got in anyway. The problem is that it gets very crowded and sometimes you can't find a spot to sit down.